So [Travis] decided to upgrade it to make use of the ever-so-common, 18650 lithium-ion battery. Not looking to purchase any components [Travis] performed this hack using simple recycled household ...

Draining a battery is easy. Just put a load across the ... a holder for a single 18650 cell, and a rocker switch to connect it all together. But wait, what’s that a TP4056 charging module ...